In the field of vehicular and mechanical repair, it is becoming increasingly common for a skilled mechanic to encounter the need to repair a vehicle or other equipment for a customer which have components made according to both metric and English measurement standards. In particular, many of today's automobiles have both nuts and bolts measured in fractions of inches as well as securement screws measured in millimeters. Often, the skilled mechanic must work in an area that is difficult to reach and even out of view. When it becomes necessary to adjust or loosen a particular nut attached to a particular bolt, the mechanic must know the size of the particular nut which he is adjusting in order to select the proper wrench to perform proper servicing of the vehicle or equipment.
Heretofore, a system of trial and error has been undertaken by a mechanic in such a predicament where he is not sure of the size of a nut secured to a bolt. In place of trial and error, the mechanic may turn to a repair manual published by the manufacturer, but often every nut and bolt is not accurately listed in such a manual according to its size.
One manner of solving the dilemma which such a skilled mechanic often finds himself would be to physically measure the diameter of a nut before providing a wrench to the nut in order to loosen a particular joint in question. Among the direct measuring devices available include an internal micrometer and extension rod which allows measurements to be estimated to one ten-thousandth of an inch. Such an internal micrometer has a vernier scale engraved on its barrel. While this micrometer is useful for precise measurement, it does not easily provide information to the mechanic as to the particular size of a nut. For example, in the English system, most nuts and bolts are measured in increments of sixteenths (or thirty-secondths) of an inch (1/16 or 1/32 inch). Such measurements do not easily translate to a decimal measurement provided by a micrometer. Also, such a micrometer is not easily manipulated by one hand in an area out of easy view on the underside of an automobile.
Likewise, if one were to use a vernier caliper to accomplish the sizing and measurement of a particular nut screwed to a particular bolt, one would not easily be able to manipulate such a caliper instrument in hard to reach places. A vernier caliper is characterized by a carriage device which rides a linear scale along a fixed elongated ruler. This carriage provides a viewing window for viewing the linearly displayed indicia. The carriage has an indexing caliper which forms a jaw with the ruler's fixed caliper. Fine adjustment is made by a screw which is mounted parallel to the line of movement of the carriage caliper. As with the internal micrometer, the vernier may give precise measurements to decimal portions of an inch, but does not easily translate to the fractional sizes common in English-measured nuts.
It appears, therefore, that micrometers and vernier calipers may provide precise measurement that is not particularly useful to solve the problem of determining the size of a standard nut which is collaring a bolt. Measurements to the ten-thousandth of an inch simply represent an overkill and go beyond the scope of what is needed to solve the problem that the skilled mechanic regularly faces.
It is an object of this invention to provide a linear measuring device which accurately indicates to a user the size of a nut which surrounds a bolt in a form of measurement which is easily recognizable according to the standards of both the English and metric systems, and helps to indentify whether an unknown nut is English or metric.
It is also an object of this invention to provide a hand measuring tool which is easily held and manipulated by one hand for placement in hard to reach or low visibility areas in order to make a measurement and a determination as to a particular size of an object.